The present invention relates to air inlet louver zone of heat and mass transfer media, or fill sheet arrangement within the direct heat exchange portion of a cooling tower. More particularly, the present invention relates to inlet louver zone attached to a fill sheet that is used in a direct heat exchange unit, which could be a cooling tower.
The heat and mass transfer media, or fill sheet arrangement, is generally vertically oriented with an evaporative liquid, usually water, coursing over the material, usually flowing downwardly, with an air stream directed usually transversely but potentially concurrent or cross current through the spaced fill sheet direct cooling section. The air interacts with the evaporative liquid for heat and mass transfer.
The integrated air inlet louver zone, hereafter called louver zone, is attached to an edge of fill sheet, is a part of fill sheet, directs airstream to fill sheet, and limits evaporative fluid from leaving the fill sheet beyond the fill sheet edge.
When a pair of fill sheets are stacked a gap forms between two fill sheets' evaporative areas but a plurality of air tunnels forms between two fill sheets' louver zones. These air tunnels, which are generally hexagonal in shape, form a straight pattern that matches well to the gap contour between the pair of fill sheets. Multiple repeats of the pair of fill sheets form a fill pack, and multiple repeats of a pair of louver zones form a louver pack within a fill pack.
The louver pack prevents evaporative liquid from splashing out of the fill pack. The louver zone's plurality of ridges and grooves are sloped downward toward the evaporative area so that the evaporative liquid that is splashed on to the louver zone is flowed back toward the evaporative area of the fill pack.
To prevent evaporative liquid from falling between two adjacent louver zones, one louver zone's plurality of ridges must align and touch adjacent louver zone's plurality of grooves so that there is no gap between the plurality of ridges and the plurality of grooves. Otherwise, two adjacent louver zones can nest and a large gap between louver zones can form within the louver pack. In this invention, during stacking, two adjacent inlet louvers are guided into an aligned location by the male indexer of the first louver zone riding on one of the guide walls of the second louver zone so that a plurality of fill sheet spacers located in the evaporative area can easily lock in the fill sheets in place with respect to each other.
For best thermal performance of a cooling tower, it is critical that the evaporative areas of the fill pack receive well distributed air streams from their louver pack. In this invention, a plurality of male indexers within the louver pack is designed so the male indexers can be positioned inside the plurality of air tunnels while preserving both the hexagonal shape and the straight pattern of a plurality of air tunnels that match so well to the gap opening shape of the evaporative areas.
For best thermal performance of a cooling tower, it is also critical that louver pack's plurality of indexing features does not incur significant air pressure drop by blocking the cooling air that travels toward the evaporative areas of the fill pack. Air pressure drop is caused by traveling air blocked by an object with a cross sectional area. A larger cross sectional area blocks more air and causes higher pressure drop. This invention uses a plurality of recessed ridges in the louver pack to decrease the size of overall cross sectional area of plurality of indexing features. A recessed ridge is located inside one of plurality of air tunnels that also houses one of plurality of male indexers. The recessed ridge lowers a small portion of the ridge of the air tunnel so that the male indexer inside the air tunnel does not have to be so tall to reach the ridge of the air tunnel. A shorter male indexer has a smaller cross sectional area, when viewed from the air tunnel opening, than a taller male indexer, and the smaller cross sectional area allows larger air passageways on both sides of shorter male indexer. A small increase in the air blockage by adding of the recessed ridge in the air tunnel is more than offset by the large increase in the air passageways. Because fill sheets, which include louver zones and a plurality of male indexers, are made from thermal forming of thin sheets of plastic, all of the fill sheet features require a draft angle of a minimum of 15°˜17°. By using the recessed ridge, the cross sectional area of the male indexers can be decreased while maintaining the minimum draft angle.
In order to further reduce the pressure drop within the air tunnel, this invention also uses curved ridge cutouts and air bypasses. In one of plurality of air tunnels that houses a male indexer, a pair of curved ridge cutouts is made to two opposing tunnel walls near the base of the male indexer. These curved ridge cutouts in the air tunnel increase the size of air passageways and allow air to go around the male indexer freely and with only a minimum air pressure drop. These curved ridge cutouts start near the base of a male indexer and opens up toward the plane of a plurality of ridges at an angle that ranges from 30° to 60° such that a portion of the two ridges at the top of the curved ridge cutouts are lowered slightly and two bypass openings are formed between the male indexer tunnel and its two adjacent tunnels. These two bypass openings allow air to travel through from two adjacent tunnels to the male indexer tunnel so that the air distribution going into the fill pack is better maintained than the design without the bypass openings.